78 COMMERCIAL FEEDING STUFFS. 



CAROB BEAN. 



The pods of this fruit are sometimes used in cattle foods, and when 

 so used in a ground condition can be most easily identified by the 

 appearance and reactions of the tannin cells. While in a growing 

 condition the contents of these cells are fluid and give a strong tannin 

 reaction with iron chlorid solution. When ripe, however, the con- 

 tents become solid and of a dark amber color, and though slow in 

 giving the tannin reaction finally produce a pronounced black color. 

 Winton recommends the use of dilute alkali, which, in the cold, colors 

 the bodies green, changing to blue-gray, while heating produces a 

 violet color. 



ANIMAL MEAL. 



The presence of this substance can be easily established by the 

 presence of striated muscle fibers, which are easily identified after 

 clearing the material with chloral hydrate and stopping down the 

 microscope substage diaphragm. 



BONE MEAL. 



This substance is identified by the characteristic lacunae and 

 canaliculi, which occur abundantly in bone tissue and which are 

 readily visible in material that has been cleared. (Plate III, fig. 4.) 



OYSTER AND CLAM SHELLS. 



To the naked eye fragments of these have a bright, shiny appear- 

 ance. Under the microscope they show no lacunae or canaliculi, and 

 with dilute hydrochloric acid give a more vigorous effervescence than 

 bone meal. 



DRIED BLOOD. 



This material has the appearance of a black powder or meal. 

 The best way to establish the identity of this substance is by the hema- 

 tin test. The method used has been to mount some of the material to 

 be tested on a slide with a few drops of water to which has been added 

 one or two tiny crystals of sodium chlorid. It is allowed to stand 

 until nearly dry, and then, after covering, a few drops of glacial ac<>t ic 

 acid are added and heated on a steam bath or hot radiator or over t he 

 micro-burner for two to five minutes, adding more acid from time to 

 time if required. Finally the slide is removed and allowed to slowly 

 cool. If the test has been properly conducted the presence of blood 

 will be shown by the presence of small plate crystals. (Plate III, 

 fig. 3.) In order to obtain crystals of good size, the final cooling 

 must be conducted slowly. 



